1. Field of the Invention
This invention relates to the production of elastomeric hydrogenated butadiene diblock copolymer having one block of high vinyl content. More specifically it relates to an elastomer of controlled molecular weight and of desired branching in the microstructure. Still more specifically it relates to an elastomeric butadiene having good resistance to oxidation and stability against ozone.
2. Related Prior Art
The most pertinent references found with regard to hydrogenated products of polybutadienes having substantial amounts of 1,2-microstructure are the articles by E. W. Duck et al which appeared in "Journal of the IRI", pages 223-227 of the October 1968 issue and pages 19-22 of the February 1972 issue. However, neither of these publications show the hydrogenation of polybutadienes having more than 60% vinyl structure.
Langer et al, U.S. Pat. No. 3,451,988 shows a method for preparing polybutadiene having higher amounts of 1,2-microstructure. However, there is no reference to hydrogenation of such products nor is there any indication of the properties or type of products produced by such hydrogenation.
A number of patents describe the hydrogenation of block copolymers in which one block is polybutadiene and another block is polystyrene, such as U.S. Pat. Nos. 3,485,787; 3,644,588; 3,686,365 and 3,827,999. However, none of these disclose the hydrogenation of a polybutadiene block high in 1,2-structure nor of a diblock copolymer in which the second block is also a polybutadiene block but predominantly of 1,4-structure.
U.S. Pat. Nos. 3,140,278 and 3,830,880 describe the preparation of butadiene diblock copolymers in which one block is predominantly 1,4-polybutadiene and the other block is predominantly 1,2-polybutadiene. The 1,4 block is prepared using a hydrocarbon solvent containing butadiene and n-BuLi. When polymerization is completed, an ether or tertiary amine is added together with additional butadiene monomer and polymerization continued to give a second block of predominantly 1,2-polybutadiene. The reverse order may also be used to produce the 1,2 block first and then adding an agent to inactivate the ether or amine so as to produce the 1,4 block. However, neither of these patents refers to the hydrogenation of such diblock copolymers nor the type of products that would be produced thereby.